The invention relates to a device for centering a geodetic instrument over a defined position mark or ground mark, having an optical sighting component arranged centrally with respect to the vertical axis of the instrument, wherein the sighting component has means for generating a visible, collimated light beam onto a ground mark or defined mark lying in the extension of the vertical axis of the instrument.
Such devices are known for geodetic instruments and are used for positioning the instrument over a ground mark, for example over a boundary stone or a position mark in a building or other structure.
A laser-theodolite in which the laser is mounted so as to be rotatable about its vertical axis and its horizontal axis is known from German Patent Specification 3,838,512. The tripod carrying the theodolite has a tribrach with a central through-clearance or aperture, through which the measuring laser can be directed at a nadir point to be determined.
The tribrach includes an automatically operating self-leveling device with electronically cooperating bubble levels.
The device described in this specification is technically highly complex and can be used only in the case of laser measuring instruments. No application possibilities above and beyond this, for example in the case of sighting targets, reflectors or the like, are possible. Conventional measuring instruments with a telescope can neither be operated nor retrofitted with this device.
In the case of other devices which have become known to date, plumb bobs or plumbing rods are used. An improvement in the positioning accuracy has been achieved by the use of an optical plummet or optical plumb bob. Such an optical plummet is arranged in the vertical axis, about which the entire instrument can be rotated, and contains an optical telescope, an eyepiece and a built-in graticule for centering the instrument over a ground mark or position mark. In use, the mark is observed with this instrument while the entire instrument is displaced over the mark until the ground mark appears in the graticule of the telescope.
These known devices have proved successful with regard to their accuracy.
Practice has shown, however, that the eyepiece arranged on the instrument is ergonomically disadvantageous. For instance, the operator must adopt a stooped position in order to continuously observe the ground mark while simultaneously displacing the instrument over the ground mark.
More recent geodetic instruments with laser measuring beams or known self-illuminating sighting marks have made it possible to carry out measurements at night or in conditions of poor light. To be able to perform an exact positioning of the instrument likewise under such conditions (in contrast to "day time measurements" or those performed in adequate light) it is necessary to illuminate the ground mark. Moreover, it is also necessary for various geodetic instruments to determine the exact distance between the ground mark and the sighting line of the geodetic instrument. Until now, this distance measurement has been carried out with conventional tape measures or divided rules and has required an additional working step.
The present invention simplifies the centering operation of a geodetic instrument of any type over a defined ground mark or position mark while simultaneously insuring ergonomically easy handling even under impeded operating conditions such as darkness or low light.
Advantageous further developments are the simplification of the distance measurement between a ground mark or position mark and the sighting line of the instrument.